Assessment of bacterial load in the indoor air of a poultry house: evaluation of the performance of real-time quantitative PCR

Title of the conference

Biomedical imaging, CHUV Research Day, February 1, 2007

Author(s)

RinsozThomas, OppligerAnne, DuquennePhilippe

Publisher

Université de Lausanne, Faculté de biologie et de médecine

Address

Lausanne

Publication state

Published

Issued date

2007

Pages

EHU-13, 27

Notes

SAPHIRID:64515

Abstract

INTRODUCTION: Workers in poultry houses are exposed to very high level of airborne micro-organisms, which have been recognized as a cause of respiratory symptoms. Estimating the airborne bacterial load of poultry houses is a key point to evaluate the risk for the workers. Traditional culture-dependent methods to quantify and identify airborne micro-organisms are limited by different factors (short-duration sampling times, inability to enumerate non-culturable or non-viable bacteria). Consequently, the assessment of bioaerosols is often underestimated. To overcome this problem, the real-time quantitative polymerase chain reaction (real-time QPCR) has been used to quantify bacteria in environmental samples. The aim of this study was to evaluate the performance of a real-time Q-PCR method to quantify the bacterial load in indoor air of poultry houses and to compare it with another non-culture-dependent method: epifluorescence microscopy.METHODS: The study was done in one chicken house and two turkeys houses. Four methods to quantify the bacterial load were tested, two non-culture-dependent methods and two culture-dependent methods: 1) Q-PCR, 2) DAPI staining and counting with epifluorescence microscopy, 3) sampling with an impinger followed by culture and 4) direct impaction on culture plates. For the Q-PCR and DAPI methods, bacteria were sampled during 3-4 hours respectively onto cellulose ester and polycarbonate filter using pocket pumps at a flow rate of 3.5l/min.RESULTS: Impaction : due to the high number of bacteria in the air, the number of colonies was too high to be counted. Q-PCR: inside chickens house, mean +/- SD : 897x106 ± 335x106 equivalent cfu/m3 and inside turkeys houses : 615x106 ± 300x106 equivalent cfu/m3. DAPI staining and counting: inside chickens house : 582x106 ± 510x106 equivalent cfu/m3 and inside turkeys houses, only one sample could be quantified with a value of 16x106 equivalent cfu/m3. Impinger and culture: inside chickens house, one value of 24x106 cfu/m3 and inside turkeys houses : 53x106 ± 38x106 cfu/m3.CONCLUSION: The results from both non-culture-dependent methods are comparable. When the impaction method is inadequate for high numbers of airborne bacteria and the value obtained with the impinger-culture method is between 10 and 20 fold lower. Real-time quantitative PCR showed his ability to estimate airborne bacterial load. It could be used in other environments to monitor bacterial load.